It is necessary in hospital and other medical environments to sterilize medical instruments with steam or ethylene oxide. Various types of sterilization containers for such medical instruments have heretofore comprised muslin wraps, various paper wraps and sterilization containers. When using the various types of wraps, medical instruments are placed in a tray, wrapped by a recommended procedure, taped, labeled and placed in a steam or ethylene oxide sterilizer. The steam or ethylene oxide penetrates the wrap and kills the bacteria. Disadvantages in the use of the sterilization wraps include the repeated expenses of the disposable wraps, potential punctures of wrapping materials thereby causing contamination, limited shelf life of the wrapped instruments and the fact that the wraps are not stackable.
Various sterilization containers have been heretofore proposed which provide a hermetically sealed container with various filters. The filters on most of these conventional containers are provided with a spring steel plate, slightly bowed with clips. The filter medium, made out of sheet stock, lies in the bottom of the sterilization container, the plate then being pressed onto the bottom and clips attached. The filter medium thus acts as a gasket with pressure being applied from the plate. As the spring steel plates are repeatedly used, the clips wear, giving the plate a loose fit into the port and a defective seal.
Other conventional sterilization containers employ a plastic cartridge that has a ring snapping over a skirt to make the seal and a retaining ring which locks into place in order to secure the cartridge to the skirt. This snap-ring system will also obviously cause a great deal of wear to the components, thereby decreasing component life and increasing the danger that no seal will be formed.
A further plastic cartridge filter system has been proposed which is in part the subject of my parent application Ser. No. 668,090. The parent application discloses a single port disposed in the container lid and a pair of ports disposed in the container bottom. Each port has a filter cartridge adapted to be fit into the port and a retainer that holds the port into place. The port has an outer member with a plurality of orifices communicating the sealed volume to the exterior. The filter cartridge has a cylindrical side member, which meets with a cylindrical side member of the port, and an inwardly extending lower annular lip member across which a filter medium is extended. The filter medium allows the passage of such gases as ethylene oxide and steam but does not allow the passage of contaminants.
A retainer ring for this system has a cylindrical side member that clamps the cartridge in place through the aid of a plurality of tabs disposed around the perimeter of the retainer ring. These tabs engage with upstanding catch members by sliding underneath laterally extending flange members. The flange members exert downward pressure on the tabs, which in turn communicate their downward pressure to the cartridge filter to make a seal.
While this port, filter, and retainer system has proven advantageous over prior art sterilization container filters, certain problems have revealed themselves. A principal problem inheres from the cylindrical design of the port, the cartridge filter and the retaining member. None of the cylindrical walls are involved in providing an adequate container seal. The sealing function is instead performed by the contact of a lower annular lip member of the cartridge with a lower annular lip member of the recessed port. The cartridge also has an upper, outwardly extending annular lip member which may make contact with the general interior surface of the container wall at the same time or even before contact of the cartridge's lower annular lip member with the annular lip member of the recessed port. Thus, the needed pressure to be exerted between the cartridge and the port annular lip member may be partially diverted to the contact between the upper cartridge annular lip member and the interior surface, to the degradation of the seal.
The retainer ring heretofore employed is also generally cylindrical in shape with an upper outwardly extending annular lip member and a lower inwardly extending annular lip member. The downward force exerted by the retaining member may be distributed along both lip members or even only on the upper lip member, thereby limiting or entirely negating any downward force to be applied between the lower annular lip member of the cartridge and the port annular lip member. This again causes problems in the quality of the seal.
Since the recessed port, cartridge and retainer ring of the prior filter are cylindrical, a substantial drag develops in inserting and removing the cartridge from the recessed port, and a like drag occurs in removing the retainer ring from the upper and inward surfaces of the filter cartridge. Both of these drags produce sources of wear that limit the effective life of both the sterilization container and the retainer ring.
In order to insure a proper seal, it has heretofore been necessary to construct filter cartridges out a relatively thick and rigid plastic. Such a thick, rigid plastic cartridge has also heretofore been necessary because a thinner or less rigid plastic would soften and leak at critical locations when subjected to hot steam, thus breaching the sterile interior of the container. A thick, rigid plastic cartridge is of course significantly more expensive than one made of thin plastic, and the rigid plastic has a lesser ability to conform to imperfections of the mating, sealing members.
A further problem with the unimproved cartridge, retainer and port system is that some difficulty is encountered in getting the tabs underneath the inwardly projecting flange portions when securing the filter to the port with the retainer ring. Further, the technician does not absolutely know how far to turn the retainer ring so that the tabs are underneath the flange portion, and there is a danger that the tabs will be rotated such that they become free on the other side of the flange portions.
A need has therefore arisen to provide a retainer and filter cartridge system that provide for a more effective seal while at the same time preventing wear to the various filter system components and controlling costs of manufacture. A need has also arisen to improve the cartridge and retainer securement means so that the retainer ring and the filter cartridge it secures can be easily positioned.